The present invention is shown and described in connection with a portable chocolate or like drink dispenser though its use is not limited to that type of dispenser alone. Drink dispensers usually employ some sort of timed metering device by which the amount of water, say, for the drink is measured out of a tank or reservoir. If a typical float system is employed to maintain a constant water level in the tank, there is always a constant head over the outlet from the tank to the metering device. But a float system requires a plumbing connection into a water supply system which more or less prevents the dispenser from being readily moved from place to place. It is for this reason that portable drink dispensers are popular and it is this type with which the present invention is concerned. In the portable dispensers no float system, of course, can be used and instead the water tank is manually filled from time to time as needed.
When no float system is used, however, so that the water level in the tank varies, it is necessary to provide some other means for supplying water at a predetermined constant rate to the metering device or otherwise the dispensed drinks will unacceptably vary in quantity and proportions as the water tank level falls. One approach uses an inner tank or "trap" at the bottom of the water tank which is vented to the atmosphere. Water from the tank is allowed to fill the trap through an inlet but once the metering device is activated, the inlet to the trap is closed so that water from the trap flows through the metering device at a predetermined rate. (The trap, of course, is always full of water before the metering device is activated.) If the inlet to the trap is not closed while the metering device is active, then water from the tank would continue to enter the trap at varying rates, depending upon the water level of the tank, and thus in turn vary the amount of water passing through the metering device and into the drink.
One typical manner of closing the inlet to the trap uses a solenoid operated valve which is closed when the metering device, usually a solenoid operated dump valve, is opened. Another way of accomplishing the same thing, a wholly mechanical system, is found in U.S. Pat. No. 2,912,143. An analogous technique is shown in U.S. Pat. No. 3,406,870 for dispensing a measured quantity of a chlorine liberating powder into a measured quantity of water. But the extra solenoid valve required in the first case is an expensive item and the various mechanical arrangements in the other cases are also expensive as well as complex. And all are subject to failure and thus costly to repair.
The primary object of the present invention, therefore, is to provide a simple, inexpensive proportioning device for a portable type drink dispenser which will assure a substantially constant amount of water or other liquid flowing from the trap or similar reservoir into the drink whenever the metering device is activated.